玩笑 + 酶，使用 mount()，document.getElementById() 在 _method 调用之后出现的组件上返回 null

问题描述：

我的 jest+enzyme mount() 测试遇到了问题.我正在测试一个功能，它切换显示组件.

I faced a problem with my jest+enzyme mount() testing. I am testing a function, which switches displaying components.

在组件之间切换:当state.infoDisplayContent = 'mission' 挂载missionControl 组件时，当state.infoDisplayContent = 'profile'- 其他组件步骤:

Switch between components: when state.infoDisplayContent = 'mission' a missionControl component is mounted, when state.infoDisplayContent = 'profile' - other component steps in:

_modifyAgentStatus () {
    const { currentAgentProfile, agentsDatabase } = this.state;
    const agentToMod = currentAgentProfile;

    if (agentToMod.status === 'Free') {
        this.setState({
            infoDisplayContent: 'mission'
        });
        agentToMod.status = 'Waiting';
    } else if (agentToMod.status === 'Waiting') {
        const locationSelect = document.getElementById('missionLocationSelect');

        agentToMod.location = locationSelect[locationSelect.selectedIndex].innerText;
        agentToMod.status = 'On Mission';
        this.setState({
            infoDisplayContent: 'profile'
        });
    }
}

当我触发这个函数时，一切正常，这个测试运行良好并且测试成功通过所需的组件:

When I trigger this function everything looks Ok, this test runs well and test successfully pass with required component:

import React from 'react';
import { mount } from 'enzyme';
import App from '../containers/App';

const result = mount(
    <App />
)

test('change mission controls', () => {
    expect(result.state().currentAgentProfile.status).toBe('Free');
    result.find('#statusController').simulate('click');
    expect(result.find('#missionControls')).toHaveLength(1);
    expect(result.find('#missionLocationSelect')).toHaveLength(1);
    expect(result.state().currentAgentProfile.status).toBe('Waiting');
});

But when I simulate onClick two times: 

test('change mission controls', () => {
    expect(result.state().currentAgentProfile.status).toBe('Free');
    result.find('#statusController').simulate('click');
    expect(result.find('#missionControls')).toHaveLength(1);
    expect(result.find('#missionLocationSelect')).toHaveLength(1);
    expect(result.state().currentAgentProfile.status).toBe('Waiting');
    result.find('#statusController').simulate('click');
    expect(result.state().currentAgentProfile.status).toBe('On Mission');
});

我得到这个断言:

    TypeError: Cannot read property 'selectedIndex' of null

  at App._modifyAgentStatus (development/containers/App/index.js:251:68)
  at Object.invokeGuardedCallback [as invokeGuardedCallbackWithCatch] (node_modules/react-dom/lib/ReactErrorUtils.js:26:5)
  at executeDispatch (node_modules/react-dom/lib/EventPluginUtils.js:83:21)
  at Object.executeDispatchesInOrder (node_modules/react-dom/lib/EventPluginUtils.js:108:5)
  at executeDispatchesAndRelease (node_modules/react-dom/lib/EventPluginHub.js:43:22)
  at executeDispatchesAndReleaseSimulated (node_modules/react-dom/lib/EventPluginHub.js:51:10)
  at forEachAccumulated (node_modules/react-dom/lib/forEachAccumulated.js:26:8)
  at Object.processEventQueue (node_modules/react-dom/lib/EventPluginHub.js:255:7)
  at node_modules/react-dom/lib/ReactTestUtils.js:350:22
  at ReactDefaultBatchingStrategyTransaction.perform (node_modules/react-dom/lib/Transaction.js:140:20)
  at Object.batchedUpdates (node_modules/react-dom/lib/ReactDefaultBatchingStrategy.js:62:26)
  at Object.batchedUpdates (node_modules/react-dom/lib/ReactUpdates.js:97:27)
  at node_modules/react-dom/lib/ReactTestUtils.js:348:18
  at ReactWrapper.<anonymous> (node_modules/enzyme/build/ReactWrapper.js:776:11)
  at ReactWrapper.single (node_modules/enzyme/build/ReactWrapper.js:1421:25)
  at ReactWrapper.simulate (node_modules/enzyme/build/ReactWrapper.js:769:14)
  at Object.<anonymous> (development/tests/AgentProfile.test.js:26:38)
  at process._tickCallback (internal/process/next_tick.js:109:7)

很明显:

document.getElementById('missionLocationSelect');

返回空值，但我不明白为什么.正如我提到的，元素通过了测试.

return null, but I can not get why. Element passes tests, as I mention.

expect(result.find('#missionLocationSelect')).toHaveLength(1);

但无法使用 document.getElementById() 捕获.

请帮我解决这个问题并运行测试.

Please, help me to fix this problem and run tests.

答

感谢 https://stackoverflow 找到了解决方案.com/users/853560/lewis-chung 和谷歌众神:

通过 attachTo 参数将我的组件附加到 DOM:

Attached my component to DOM via attachTo param:

const result = mount(
    <App />, { attachTo: document.body }
);

将我的方法中的错误字符串更改为与元素对象一起使用的字符串

Changed buggy string in my method to string which works with element Object

agentToMod.location = locationSelect.options[locationSelect.selectedIndex].text;` : 

_modifyAgentStatus () {

    const { currentAgentProfile, agentsDatabase } = this.state;
    const agentToMod = currentAgentProfile;

    if (agentToMod.status === 'Free') {
        this.setState({
            infoDisplayContent: 'mission'
        });
        agentToMod.status = 'Waiting';
    } else if (agentToMod.status === 'Waiting') {
        const locationSelect = document.getElementById('missionLocationSelect');

        agentToMod.location = agentToMod.location = locationSelect.options[locationSelect.selectedIndex].text;
        agentToMod.status = 'On Mission';
        this.setState({
            infoDisplayContent: 'profile'
            });
        }
    }

玩笑 + 酶，使用 mount()，document.getElementById() 在 _method 调用之后出现的组件上返回 null

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